使用 neo4j OGM 按属性名称查找节点

Question

我的 SkillCluster class 如下

public class SkillCluster {
    @Id @GeneratedValue
    private Long id;
    private String Name;
    private String CleanedText;

    @Relationship(type = "BelongsTo", direction = Relationship.INCOMING)
    private Set<Skill> contains = new HashSet<>();
}

对应的DAO class

import org.neo4j.ogm.session.Session;
import com.models.GenericDAO;

public class SkillClusterDAO extends GenericDAO<SkillCluster>{
    public SkillClusterDAO(Session session) {
        super(session);
    }

    protected Class<SkillCluster> getEntityType() {
        return SkillCluster.class;
    }   
}

和我的 GenericDAO class 作为

public abstract class GenericDAO<T> {
    private static final int DEPTH_LIST = 0;
    private static final int DEPTH_ENTITY = 1;  
    private Session session;

    public long filterCount(Iterable<Filter> filters){
        return session.count(getEntityType(), filters);
    }

    public T find(Long id) {
        return session.load(getEntityType(), id, DEPTH_ENTITY);
    }

    public T find(String name) {
        return session.load(getEntityType(), name, DEPTH_ENTITY);
    }

    public void delete(Long id) {
        session.delete(session.load(getEntityType(), id));
    }

    public void createOrUpdate(T entity) {
        session.save(entity, DEPTH_ENTITY);
        //return find(entity.id);
    }

    protected abstract Class<T> getEntityType();

    public GenericDAO(Session session) {
        this.session = session;
    }
}

我想通过匹配节点属性 Name 来获取集群节点

skillSessionFactory = new SessionFactory(skillConfiguration, "com.skill.models");
skillSession = skillSessionFactory.openSession();

skillClusterDAO = new SkillClusterDAO(skillSession);
SkillCluster clusterNode = skillClusterDAO.find(cluster_name);

我收到以下错误 -

java.lang.IllegalArgumentException: Supplied id must be of type Long (native graph id) when supplied class does not have primary id - com.models.SkillCluster

Answer 1

您出现此错误是因为 name 属性不是 Long。

即使你的名字属性也是 Long，它也不会工作，因为它会被提取到错误的节点。

session.load(...) 适用于内部节点 ID，或属性标记为 @Id 或主索引 @Index(primary = true).

如果您需要通过属性而不是主键来查找节点，您可以使用 session.loadAll(...) 和过滤器。

public abstract class GenericDAO<T> {

  ...

  import java.util.Collection;
  import java.util.Optional;
  import org.neo4j.graphdb.GraphDatabaseService;
  import org.neo4j.ogm.cypher.Filter;
  ...

  public T find(Long id) {
    return session.load(getEntityType(), id, DEPTH_ENTITY);
  }

  public T find(String name) {
    final String propertyName = "name";
    Filter filter = new Filter(propertyName, name);

    Collection<T> results = session.loadAll(getEntityType(), filter, DEPTH_ENTITY);

    if( results.size() > 1)
      throw new CustomRuntimesException("Too results found");

    Optional<T> entity = results.stream().findFirst();

    return entity.isPresent() ? entity.get() : null;
 }

 ...

}

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